MacBook Pro 17" A1212 Hard Drive seems to be failing?

I have a Macbook Pro 17" Model A1212 purchased in 2006. I replaced the original hard drive 2-3 years ago with a Seagate 750GIG Sata 2.5". I am now experiencing problems with it waking from sleep with the lid open whereby it freezes, other times when I close the lid and return opening the lid I get the spinning wheel and have to force shutdown. Times when I simply move it from one location to another, I unplug the power cord, move it to another room to find it frozen.

It is old, I recognize that, but I'm having a hard time parting with a 17" display notwithstanding the sticker shock of a new one.

I think the hard drive is now done again, but before I throw good after bad, how can I tell if it's the hard drive or something like the logic board that's given up the ghost?

We have the screen up with all the sentence after sentence with information on...and I do not understand what any of that means...what do we do next? How do we proceed to fix our 17" A1212 Macbook Pro. We installed the new hard drive and installed more memory...now we can not get our computer to work.

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